FIG. 1 illustrates an internal circuit of a color TV with a conventional satellite broadcast receiver internally installed. As shown in this drawing, the internal circuit includes: a satellite broadcast receiving part 100 for outputting video and audio signals after receiving and processing satellite broadcast signals; a TV receiving section 200 for outputting video and audio signals after receiving and processing TV broadcast signals; a video selecting switch 300 for selecting one signal form among the output video signals of the satellite broadcast receiving section 100 and the TV receiving section 200 and the video signal externally input; a video signal processing part 310 for displaying to a cathode ray tube (CRT) after processing the video signals selected by the video selecting switch 300; an audio selecting switch 330 for selecting one signal form among the audio signals of the satellite broadcast receiving section 100 and the TV receiving section 200, and the outer input audio signal; and audio signal amplifiers 340,350 for outputting to speakers 360,370 after amplifying the audio signals selected by the audio selecting switch 330.
The satellite broadcast receiving section 100 includes: a satellite broadcast tuner 110 for selecting a desired channel for the satellite broadcast signals based on the tuning voltage of a satellite broadcast tuning part 115; an a frequency modulation (FM) detecting part 120 for outputting base band signal after FM-detecting the signal of the channel selected by the satellite broadcast tuner 110; a low pass filter 130 for passing only the base band video signals of the FM detecting section 120; a satellite broadcast video signal processing section 140 for processing the video signal passed through the low pass filter 130; a band pass filter 150 for passing only the audio carriers from the base band signals of the FM detecting part 120; audio tuning parts 160,165 for selecting the desired signals after tuning the audio carriers passed through the band pass filter 150; audio bandwidth selecting parts 166,167 for selecting narrow band or wide band in accordance with the bandwidths of the output signals of the audio tuning parts 160,165; satellite broadcast audio FM detecting parts 170,175 for FM-detecting the output signals of the audio bandwidth selecting parts 166,167; and satellite broadcast audio signal processing sections 180,185 for outputting outputs after processing the output signals of the satellite broadcast audio FM detecting parts 170,175.
The TV receiving section 200 includes: a TV tuner 210 for selecting a desired channel for TV broadcast signals based on the tuning voltage of a TV broadcast tuning part 215; a TV amplitude modulation (AM) detecting part 220 for outputting base band signals after AM-detecting the signals of the channel selected by the TV tuner 210; a low pass filter 230 for passing only video signal among the base band signal of the TV AM detecting part 220; a TV broadcast video signal processing part 240 for outputting composite video signals after processing the video signals passed through the low pass filter 230; band pass filters 250,255 for passing only audio carriers among the base band signals of the AM detecting part 220; and TV FM detecting parts 260,265 for FM-detecting the audio carriers of the band pass filters 250,255, and for supplying them to TV audio signal processing parts 270,275.
The color TV with the conventional satellite broadcast receiver internally installed is constituted as described above, and will be described as to its operations below.
First, the satellite broadcast receiving section 100 controls the satellite broadcast tuner 110 based on the tuning voltage of the satellite broadcast tuning part 115 in order to receive the signal of the desired channel among the satellite broadcast signals, and the FM detecting part 120 carries out FM detections to obtain the base band signal.
The base band signal which is outputted from the FM detecting part 120 is supplied to the low pass filter 130 by which the audio carriers are removed, and only the video signals are passed. After passing through the low pass filter 130, the video signal is supplied to the satellite broadcast video signal processing part 140 where the signal undergoes a de-emphasis process and an energy dispersion removal process, before being supplied to the video selecting switch 300 in the form of composite video signals.
The base band signal which is output form the FM detecting part 120 of the satellite broadcast receiving section 100 is supplied to the band pass filter 150 where the video signal is removed, and only the audio carriers are passed through, with the audio carriers being then supplied to the audio tuning parts 160,165 so as for an audio tuning to be carried out.
Under this condition, the reason for carrying out the audio tuning is that the frequency of the audio carriers is different in the satellite broadcast from that of the TV broadcast, and therefore, a separate audio tuning has to be carried out in order to receive the desired audio signals.
Accordingly, the audio carrier signals which have undergone the audio tunings at the audio tuning parts 160,165 are allowed to have wide band width or narrow band width by the audio band width selecting parts 166,167. Then the signals are supplied to the satellite broadcast audio FM detecting parts 170,175 to undergo FM detections, and then, the signals are subjected to an audio de-emphasis process and an audio level compensation, as well as being processed by the satellite audio signal processing parts 180,185 based on the different methods of each country, before being supplied to the audio selecting switch 330.
In the satellite broadcast as in the TV broadcast, audio broadcast signals are sent out based on the one or two-carrier method, and therefore, the audio signals for one or two channels are processed. Meanwhile, in the TV receiving section 200 also, the tuner 210 is controlled based on the tuning voltage of the tuning section 215, and then, the desired channel of the desired band video high frequency, ultra high frequency is selected. Then, an AM detection is carried out by the TV AM detecting part 220, and then a signal consisting of video signals and audio signals is outputted.
If the base band signal which is output from the TV AM detecting part 220 is supplied to the low pass filter 230, the audio carriers are removed, and only the video signal is passed through. If the video signal which has passed through the low pass filter 230 is supplied to the TV broadcast signals processing part 240, the signal is processed into composite video signal which is supplied to the video selecting switch 300.
If the base band signal which is output from the TV AM detecting art 220 is supplied to the band pass filters, the video signals are removed, and only the audio signals pass through. Then the audio carriers which have passed through the band pass filters 250,255 are supplied to the TV FM detecting parts 260,265 to be FM-detected. Then the signals are subjected to a de-emphasis process, and are processed by the TV audio signal processing parts 270,275 based on the different methods of each country, so that audio signals should be output to be supplied to the audio selecting switch 330.
Under this condition, in the TV broadcast also, two-carrier audio signals are sent out, but, in the TV broadcast unlike the satellite broadcast, the carrier frequencies are fixed, and therefore, the audio tunings are not carried out, but the outputs of the band pass filters (as it is) are supplied to the TV FM detecting parts 260,265.
Then the video and audio signals output from the satellite broadcast receiving section 100 and the TV receiving section 200, and the outer input video and audio signals are respectively selected by the video selecting switch 300 and by the audio selecting switch 330, and then, they are supplied through the video signal processing part 310 and the audio signal amplifiers 340,350 to a CRT 320 and to speakers 360,370.
In such a color TV with a conventional satellite broadcast receiver internally installed, the tuning parts 115,215 which supply the tuning voltages are separately provided to both the TV receiving section and the satellite broadcast receiving section. Further, separately provided are also the low pass filters 130,230 for removing audio carriers and for passing only video signals among the base band signal, and the band pass filters 150,250, 255 for removing video signals and for passing only audio signals among the base band signals. Further, the FM detecting parts 170,175,260,265 and the audio signal processing parts 180,185,270,275 are also separately provided.
That is, the functional blocks performing the same functions and operations are separately designed for both the satellite broadcast receiving section and the TV receiving section, and therefore, the circuits are complicated, with the result that the manufacturing cost is increased.